This invention relates to nuclear reactor maintenance apparatus and more particularly to nuclear reactor inspection apparatus for remotely determining spacing between two members.
Conventional pressurized water reactors comprise a reactor vessel with a reactive core disposed therein which produces heat in a manner well understood in the art. A water coolant is circulated through the reactor vessel and in heat transfer relationship with the core so that heat is transferred from the core to the water coolant. The reactive core generally comprises a plurality of fuel assemblies comprising nuclear fuel. The fuel assemblies are surrounded by a plurality of vertical metal baffle plates that define the outer limits of the core. Although the baffle plates are joined together to form an outer perimeter for the core, the individual baffle plates are not welded together. Since the baffle plates are not welded together, small gaps may exist between two adjacent baffle plates. Because the baffle plates serve to direct the flow of reactor coolant water through the reactor core, the small gaps between the baffle plates do not detract from the performance of this function. However, since a substantial pressure differential may exist across the baffle plates, it is possible for small streams of high velocity reactor coolant to be established through the gaps between these baffle plates. These streams of reactor coolant can cause vibrations in the fuel assemblies or otherwise damage the fuel assemblies. Therefore, what is needed is apparatus for determining the size of the gap between each baffle plate so that those gaps that are too large may be reduced.